To test the hypothesis that an imbalance in salt-retaining and salt- losing steroid hormones is involved in the pathogenesis of essential hypertension, these hormones will be measured in plasma and urine by radioimmunoassay and their production rates determined. Steroid radioimmunoassays are simple enough to make this survey in essential hypertension feasible, yet sensitive and specific enough to do the job. Measurements will be done with different salt intakes, variations in posture, and following ACTH administration to test for aberrations in response to normal physiological stimuli. ACTH and renin levels will be measured simultaneously to evaluate control mechanisms. By comparing values in patients with those from normotensive controls, the role of salt-retaining and salt-losing steroids in essential hypertension might be clarified.